The following two equilibrium reactions can be written for aqueous carbonic acid, H₂CO₃(aq):

For each reaction write the equilibrium constant expression. By using Le Châtelier’s principle we may naively predict that by adding H₂CO₃ to the system, the concentration of CO₃^2- would increase. What we observe is that after adding H₂CO₃ to the equilibrium mixture, an increase in the concentration of CO₃^2- occurs when [CO₃^2-] ≪ K₂; however, the concentration of CO₃^2- will decrease when [CO₃^2-] W K₂. Show that this is true by considering the ratio of [H⁺]/[HCO₃^-] before and after adding a small amount of H₂CO₃ to the solution, and by using that ratio to calculate the [CO₃^2-].

Transcribed Image Text:

H₂CO3(aq) HCO3(aq) H(aq) + HCO3(aq) → H+ (aq) + CO3² (aq) K₁ K₂